


To Love Yourself (and your brother and his twin)

by Askellie (NadaNine)



Category: Undertale (Video Game)
Genre: Ecto-Genitalia (Undertale), Fontcest, Fontfest - Freeform, Foursome, M/M, Negotiations, Polyamory, Rough Sex, Sanscest - Freeform, Voyeurism, papcest - Freeform
Language: English
Status: Completed
Published: 2016-08-10
Updated: 2016-08-10
Packaged: 2018-08-07 21:31:55
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,463
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7730443
Author URL: https://archiveofourown.org/users/NadaNine/pseuds/Askellie
Summary: <blockquote class="userstuff">
              <p>A giftfic for Undertailsoulsex based on her amazing fic, <a href="http://archiveofourown.org/works/6424108">To Love Yourself</a>.</p>
<p>Red wants his brother to feel included. Sans wants Red to be happy. Somehow they're going to make this work.</p>
            </blockquote>





	To Love Yourself (and your brother and his twin)

**Author's Note:**

  * For [undertailsoulsex](https://archiveofourown.org/users/undertailsoulsex/gifts).
  * Inspired by [To Love Yourself](https://archiveofourown.org/works/6424108) by [undertailsoulsex](https://archiveofourown.org/users/undertailsoulsex/pseuds/undertailsoulsex). 



> This is a non-canon 'what if' exploration of how things could have turned out. c: Mostly because I have wanted this foursome forever, damnit.

Sans had picked the best, or possibly the worst possible moment, to finally ask the question. He had Red straddled backwards across his lap, holding both of the scarred skeleton’s femurs wide and slightly raised so that Papyrus could get enthusiastically down to business between his legs. Between them, they’d already gotten Red off once already, so he was past the point of distracted desperation and was just comfortably aroused and exceedingly relaxed. He felt completely spoiled, being the sole recipient of the two brother’s attentions, with Sans skilfully gliding his fingers up the length of Red’s spine as though he was playing a particularly precious instrument. Every so often his teeth would nip fondly at the base of Red’s neck and the span of his clavicle, the little jolts of pain making Red sigh blissfully.

Basically, he had been thoroughly primed to agree to just about anything, which was surely what Sans had intended.

“Hey Red,” Sans murmured, phalanges tightening delightfully around one of the most sensitive discs on his spine – the same one Flowey had put a hole in months ago, which had now mostly healed over. Red groaned at the residual tingle, pitching the noise affirmatively to show he was paying attention. “We’ve noticed that…well, you and your bro are back together now, right?”

Sans spoke softly, carefully, like he was hesitant to broach the subject but pushing on all the same. Red couldn’t blame him. He was still pretty touchy about it himself. He squirmed, not entirely from the pleasant ministrations. “Y-yeah? Why? It’s not a problem, is it?”

Red didn’t think it should be, given how many other partners Sans was also juggling, but come to think of it Red had never asked, he’d just assumed…but surely Sans wouldn’t hold that against him, right? It was _Papyrus_ , Red’s Papyrus. Surely Sans understood.

“No, course not,” Sans reassured him soothingly, his hold on Red clinching a little tighter, easing away that brief stab of concern. “I’m glad, actually. I know you need him. Pretty sure he needs you too.”

Red made an ambivalent sound. He wasn’t sure how true that was, exactly, but there was definitely something between them still, though it was perhaps a little too damaged and bitter to call need.

“It’s just…Pap and I were talking about it,” Sans continued, and here Papyrus looked up briefly to offer his brother and Red a reassuring smile before turning his attention back to the sensitive mound of Red’s pubis. “And we were wondering if you’d ever…well, if you’d ever thought about asking him to join us?”

Red promptly flushed the colour of his namesake. Papyrus’s tongue had started to delve inside him in long, sinuous strokes, and coupled with Sans asking him that question…

“Ah…” he gasped in place of answering, because…well, of course, he’d thought about it. It was awkward, juggling time with his brother, having to be more discreet when Edge was in the house because Red didn’t want to flaunt his new relationships in his brother’s face, like rubbing salt in the wound of their separation from each other. Edge wasn’t stupid. He knew what Red was doing with the other Sans and Papyrus, and Red had told Edge he wasn’t breaking off his new bonds despite his brother’s return. He’d had to work up all his relatively meagre courage to say that to his brother, only to receive a non-committal grunt in return, and henceforth Edge had basically just ignored that part of Red’s affairs, saying nothing about the nights Red spend in the other skeleton’s room, and only staring critically every time one of them expressed a thoughtless, affectionate gesture in one of the common areas before sheepishly pulling back.

The whole situation was uncomfortable, but Red didn’t know how to fix it.

Except, of course, in the ideal fantasy scenario where his brother truly didn’t care, because he too was involved. Where Sans and Papyrus included his sullen, angry younger brother in their seemingly boundless kindness and passion; where Edge could experience a little of the healing and support Red had become so reliant on…but that was just a dream, of course, because his brother was broken and brittle and so cagey still, as if nothing at all could be trusted least of all this universe where everything was too good to be true. Red himself was having a hell of a time dealing with that; he wouldn’t wish it on anyone else. Besides, just because he loved his brother didn’t mean Sans and Papyrus were obliged to.

Sans was still waiting for an answer, and even Papyrus slowed down enough to give Red a moment to think, as if his blush hadn’t already given it away. “I…I’ve t-thought about it.”

Sans pressed up against the side of Red’s skull, his voice soft and gentle, seductive. “Would you like him to?”

Papyrus abruptly changed from licking to sucking, his mouth applying tight, throbbing pressure to Red’s pelvis, making the smaller skeleton yelp and buck wildly in abandon. Sans had to shift his grip to hold Red steady, restraining him in such a way that he felt almost helpless, almost controlled and claimed the way his brother had once done for him and even now Red found it breathtaking.

“Yes!” he wailed, writhing in Sans’s grip, practically shouting the answer that he otherwise wouldn’t have dared to even whisper, and he was so overcome with his building climax that he didn’t even see the way Sans grinned in victory as he held Red lovingly through his shuddering orgasm.

* * *

Red was nervous, sweating visibly, even more so than usual. He looked distinctly uncomfortable, straddled across his brother’s lap like he was unsure of his right to be there. Edge had better composure, but his rigid posture was telling. He didn’t seem to know where to put his hands, and eventually mimicked Papyrus’s hold on Sans who was also cradling his smaller brother, hands on Sans’s femurs to help him stay balanced.

“Just go at your own pace,” Sans offered, trying to make it sound like more of a suggestion than a direction. Edge seemed to take offence to the latter. Demonstratively, he leaned in towards Papyrus, and the two of them shared a familiar, warm grin before their mouths met with a clink of teeth before parting to allow mutual access to each other’s tongues.

He tried not to let himself get distracted, but Papyrus wasn’t making it easy. He knew all the ways in which Sans enjoyed being kissed – slow and wet and lingering, his long, surprisingly dexterous tongue winding around Sans’s and squeezing tightly. Sans moaned into his brother’s mouth, instinctively moving closer, feeling the familiar thrum of magic and arousal building between them. It made him regret not having shed his clothes before starting, but Red’s uncertainty and Edge’s aloof nature made him aware that they would need to take things slowly.

Or so he’d thought, but a soft sound interrupted his reverie, and when he glanced to the side he was surprised to see Edge was devouring Red’s mouth with such intensity that the smaller skeleton was bent backwards at an angle that looked almost painful, barely able to hold against the hungry urgency of it. Edge’s sockets were closed, the scowling expression on his face almost pained with desperation. Red;s were blown wide with small whimpering sounds tearing from his throat, his body shuddering, but he was gripping the collar of Edge’s shirt just as vehemently. The rest of the world might as well not exist, they were so wrapped up in each other.

“Huh,” Sans mused, curling his arms around Papyrus’s neck. “Look at that. I’m almost jealous.”

Papyrus nuzzled at his collar. “Does that mean you’d prefer me to be more…forceful?”

Sans blushed slightly. It wasn’t something he tended to ask for, since it could easily backfire if it triggered the wrong memory, but though his brother was endlessly gentle and careful with him, Sans sometimes craved the rough, more callus way Grillby would bend him over one of the benchtops and fuck him senseless. “Maybe.”

Papyrus’s eyelights gleamed playfully, and Sans had a feeling that there was a hint of competitive spirit in the way that his brother suddenly flipped their positions and threw Sans face-down onto the bed. He hardly had a moment to orient himself before Papyrus was pressing down on top of him, hips rutting against Sans’s tail bone, teasing at the space beneath it.

“Oh fuck, yes!” he gasped, more loudly than he’d meant to, but it was hard to think of anything except possessive weight of his brother above him and the way his pelvis was poised on the edge of the mattress, the soft edge digging into the space where his magic was starting to form.

A heavy impact shook the mattress, and when Sans angled his face up from the comforter he saw Red had been pinned down in a simmilar position on the opposite side of the bed, his arms yanked up and restrained roughly behind his shoulder-blades, but his expression was one of dazed, euphoric pleasure.

“Fuck, yes, Boss, please!” Red panted, writhing beneath his brother’s ministrations. Sans grinned, using his own free arms to drag himself forward until his skull was nearly level with Red’s own. Red blinked at him, mouth open and saliva dripping with abandon down his chin, delightfully accessable for Sans to lean in and kiss him thoroughly. There was a distinctive, new taste in Red’s mouth that must have been left behind by his brother, and Sans chased the flavour thoughtfully, trying to pin it down. It was sharp and spicy, like cayenne, lingering on his tongue and prickling at the magical nerves.

Red whined in distress when Sans pulled away, and Sans wasn’t too pleased to do so either, but he felt compelled to check Edge’s reaction. It was one thing for Edge to have agreed to the idea of joining his cross-universe counterparts during intimacy, but another to actually go through with it. From what he’d gathered, polyamory wasn’t as common in the other universe, or perhaps just wasn’t as viable when most of the population were aggressive, selfish assholes. He was prepared for the possibility that Edge might react badly to the sight of his brother being pleasured by another.

Edge surprised him again, however. The taller skeleton’s face seemed oddly contemplative, screwed up in thought. Sans silently arched a brow at him, hoping it might coax out a more emphatic reaction for better or for worse, and it did. Edge leaned forward, his weight pressing hard into Red as he did, and, with more gentleness than Sans would have expected, he felt claws cup the back of his skull and pull him back against Red in a silent demand that they continue.

(He’d tried not to think too much about the way Edge’s phalanges had been sharpened the same way his teeth hard, but now Sans could feel the razor edges pricking the back of his head, tantalising and dangerous, and the thought of them didn’t unnerve him as much as it should have. He suspected he and Red had more in common than he’d originally guessed.)

He was more than happy to return his attention to Red’s mouth, and he vocalised his approval in a contented purr as he nipped around the corners of Red’s teeth aggressively enough to cause the little thrills of pain he knew Red enjoyed. He was rewarded with wordless groans of appreciation and the delightful way Red’s eyelights rolled back in pleasure. Red strained forward, yearningly, trying to encourage Sans to delve further into his mouth, but he couldn’t wriggle out from under his brother’s weight and after a moment Sans realised he couldn’t either. Papyrus had divested him of his shorts, and had taken a firm grip on Sans’s spine to keep him still whilst his fingers skilfully stroked along the underside of his coccyx.

“Ah-! Pap…” Sans wanted ease back and impale himself fully on his brother’s fingers, but Papyrus refused to let him, keeping Sans locked in place and thrusting mercilessly into his pelvic inlet until Sans’s magic solidified in a dripping pussy desperate to be filled. He tried spreading his femurs, presenting himself, but his brother immediately changed the angle of his stokes and just let his phalanges slide along the length of his slit. The smooth knobs at each finger joint provided an excruciating torment as they grazed against everywhere except the places they would be best served; against his clit or inside his cunt. Sans spluttered in protest, trying to compel Papyrus to take him, swiftly and completely, but his brother seemed content to deny him.

“Fuck! Boss! Hnngh!” Red practically screeched, his body convulsing, and though Sans didn’t have the best angle to observe he could tell by the demanding thrust of Edge’s hips that his counterpart was getting fucked already, hard and fast and brutal and deep and _it wasn’t fair what the hell, Papyrus!?_

“Bro, please,” he pleaded, because his core was aching, the inner muscles clenching futilely, and he needed something _in_ him.

“Patience, brother,” Papyrus murmured, his voice low and simmering with a glee Sans rarely heard from him.

Normally Sans could be exactly that – patient – but he could hear the wet, lewd sounds of Edge’s cock ramming into whatever opening Red had conjured, and hear Red wailing and begging for more, his pleasure staring to peak when Sans’s was reaching the point of painful urgency, and of all the possible times for his brother to deny him this was the worst. He just wanted to join Red in ecstasy, to come apart under Papyrus’s hands as Edge watched and to be turned into the same mindless, drooling mess Red had become.

“Pap!” he begged, spine arching, hips rocking, trying to find any sort of satisfaction against the corner of the mattress, but he couldn’t find the right angle. “Please, please, come on, fuck me, I need it! Papyrus, please!”

He forgot at the last moment that ‘Papyrus’ could potentially mean two people in the room, forgot that while Red’s voice is usually pitched at a huskier timbre, their voices were nearly identical, and so it nearly startled him that Edge shudders violently, cursing under his breath, and with one final lunge emptied himself inside his brother in the throes of a powerful orgasm.

The way Papyrus stroked his hip made him think all the pleading he’d forced out of Sans had been very deliberate. “All right, brother, since you asked so nicely.”

Frankly, as long as he got Papyrus’s cock inside him right this minute, he couldn’t bring himself to care.


End file.
